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DNA: A ‘New’ Crime-solving Molecule?

Anyone who has ever watched “Law and Order” or “CSI” knows: obtaining and analyzing DNAevidence features prominently in many of its fictional criminal cases. But leaving such TV dramatizations aside, over the last two decades, DNA evidence has come to play an increasingly routine and important role in the U.S. law enforcement and justice systems. Technological innovations within science and social policy have both played a role in this process.

The DNA profile technique, introduced by Sir Alex Jeffreys in England in the 1980s, enabled forensic scientists to exploit the small difference (0.01%) that exists between humangenomes as a kind of ‘genetic fingerprint.’ DNA profiling identifies repetitive (“repeat”) sequences that are highly variable among non-related individuals. Smaller amounts of biological material can be subjected to such DNA ‘fingerprinting’ because of the development and use of PCR (polymerase chain reaction). Devised by Nobel-prize winning American biologist Kary Mullis, PCR enhances the ability of law enforcement to get meaningful DNA information out of what is often a minimal (or degraded) biological sample found at a crime scene.

But the most significant use of DNA evidence has been enabled not by technology but by social policy – specifically, the development and expansion of so-called “DNA databases.” In 1989, the Virginia General Assembly became the first American legislature to pass laws that required sex offenders and violent felons to submit DNA samples for inclusion in a DNA databank. Within a decade, the other 49 states passed laws requiring the collection of DNA samples from certain criminals for the same purpose. Individual DNA profiles can now be compared to profiles already cataloged through both state and federal DNA databases to identify criminal offenders.

Since the mid-1990s DNA evidence has been used to exonerate many individuals who were wrongly convicted in criminal cases where no (or limited) biological analysis of evidence was available during their trial. The non-profit Innocence Project, spearheaded by lawyers Peter Neufeld and Barry Scheck, reports that, since the 2000, 235 people have been exonerated through the introduction of DNA evidence. Neufeld and Scheck note that the overwhelming majority of those exonerated are African Americans.

DNA, then, is not a ‘new’ crime-solving molecule, but it has become an increasingly powerful one. Federal task forces are now focused on making its power more reliable and accessible. They recommend providing more training and assistance to law enforcement officials, lawyers, and victims, and also, updating technology in public crime labs to ensure the accuracy and speed of DNA evidence analysis.